I don't know, but it's seemingly fixed. 1. removed virtualbox-bin (6.0.10-1) installed virtualbox-host-dkms (6.0.10-1) installed virtualbox (6.0.10-1) Rebooted into a kernel that worked a few days back. Reinstalled the extensions. When opening a shared folder the Windows 7 guest restored from a snapshot still crashed and the machine ignores USB. 2. removed virtualbox (6.0.10-1) removed virtualbox-host-dkms (6.0.10-1) installed virtualbox-bin (6.0.10-1) downgraded systemd-libs (242.84-1 -> 242.32-3) downgraded systemd (242.84-1 -> -> 242.32-3) downgraded lib32-systemd (242.84-1 -> 242.32-1) downgraded systemd-sysvcompat (242.84-1 -> 242.32-3) Rebooted into a kernel that worked a few days back. Reinstalled the extensions. When opening a shared folder the Windows 7 guest restored from a snapshot still crashed and USB is still missing. 3. reinstalled systemd-libs (242.32-3) reinstalled systemd (242.32-3) reinstalled lib32-systemd (242.32-1) reinstalled systemd-sysvcompat (242.32-3) reinstalled virtualbox-bin (6.0.10-1) Deleted the Virtualbox config, the guest and the shared folder: ~~~ $ sudo rm -Ir /mnt/winos7/* /home/rocketmouse/.VirtualBox/ ~~~ Restored the Virtualbox config, the guest and the shared folder: ~~~ # cd /home/rocketmouse/ && time tar xf /mnt/u3.fantec2/2019-Jul/s3.archli*600_*tar.gz home/rocketmouse/.VirtualBox; echo $?; cd /mnt/winos7/ && time tar xf /mnt/u3.fantec2/2019-Jul/arcwinos7*600_*tar.gz; echo $? # mv -i /home/rocketmouse/home/rocketmouse/.VirtualBox/ /home/rocketmouse/; echo $? ~~~ Rebooted into a kernel that worked a few days back. Reinstalled the extensions. Still no USB device available, at least this still worked yesterday. The good news, now I can open the shared folder, which OTOH gains nothing, if I can't connect portable devices via USB in the first place. I shut down the Windows 7 guest, restarted it, again no USB, but access to the shared folder is working. 4. ~~~ $ sudo pacman -Syu [snip] Packages (4) lib32-systemd-242.84-1 systemd-242.84-1 systemd-libs-242.84-1 systemd-sysvcompat-242.84-1 [snip] ~~~ Rebooted into the same kernel. I didn't restore the Windows guest, even not from a snapshot. USB is still missing, access to a shared folder still works. ~~~ $ grep upgrade /var/log/pacman.log [snip] ~~~ The log seems to be no help. The guest's settings show that USB 2.0 is enabled. Strange: ~~~ $ ls -hAl /dev/vbox* crw------- 1 root root 10, 57 Jul 28 15:28 /dev/vboxdrv crw------- 1 root root 10, 56 Jul 28 15:28 /dev/vboxdrvu crw------- 1 root root 10, 55 Jul 28 15:28 /dev/vboxnetctl ls: cannot open directory '/dev/vboxusb': Permission denied $ sudo ls -hAl /dev/vbox* crw------- 1 root root 10, 57 Jul 28 15:28 /dev/vboxdrv crw------- 1 root root 10, 56 Jul 28 15:28 /dev/vboxdrvu crw------- 1 root root 10, 55 Jul 28 15:28 /dev/vboxnetctl /dev/vboxusb: total 0 drwxr-x--- 2 root vboxusers 80 Jul 28 15:20 002 drwxr-x--- 2 root vboxusers 60 Jul 28 15:20 004 $ id uid=1000(rocketmouse) gid=1000(rocketmouse) groups=1000(rocketmouse),10(wheel),50(games),91(video),92(audio),93(optical),95(storage),98(power),100(users),150(wireshark),992(realtime),1003(vmanusers) $ sudo usermod -a -G vboxusers rocketmouse ~~~ Logged out and in. ~~~ $ id uid=1000(rocketmouse) gid=1000(rocketmouse) groups=1000(rocketmouse),10(wheel),50(games),91(video),92(audio),93(optical),95(storage),98(power),100(users),108(vboxusers),150(wireshark),992(realtime),1003(vmanusers) ~~~ USB access is back. Accessing a shared folder doesn't cause a crash anymore. Everything seems to be fixed. I've done absolutely nothing on my machine, other than upgrading from official repositories, that could have broken Virtualbox's access to a shared folder in the first place. Actually I don't know what did cause the issue, neither what solved it.